During catheter ablation of atrial fibrillation (CAAF), unfractionated heparin (UFH) dosage monitoring through the activated clotting time (ACT), may be challenging in patients under uninterrupted oral anticoagulants (OAC).

We aimed to develop a mathematical model for accurate adaptation of UFH dose whatever the uninterrupted OAC regimen.

Forty patients undergoing CAAF under uninterrupted OAC were prospectively included to complete 4 groups of 10 patients receiving Fluindione, Dabigatran, Rivaroxaban or Apixaban. UFH dose was adapted as standard of care in our center, through repeated ACT measurements, to reach a target of >250sec. Using the ACT and corresponding UFH dose values we developed a mathematical model for predicting the UFH dose based on the very first ACT values. The validity of the model was tested by comparing the predicted (by the model) and observed (standard of care) ACT values.

Our model was built on 2 equations describing:.

– the HNF dose as a function of time: e’(t)=−k e(t)+vi;

– ¹the ACT as a function of time: ACT (ti+1)=ACT (ti)+a(Ri+vi/k−e(ti+1).

¹The mean linear regression correlation coefficient between predicted and observed ACT values is 0.84±0.15.

Mathematically, a simple phenomenological model has been developed and shows highly accurate prediction of the observed ACT values. It may be used on a routine basis during CAAF ablation procedures. ¹e’(t) is the first derivative of e(t) which is the estimated quantity of UFH present in the virtual compartment as a function of time; vi is the constantly infused UFH dose at time i; R takes into account potential additional UFH bolus administration; the parameters k and a determined using the first 3 ACT measurements, are related respectively to the individual elimination and anticoagulant activity of UFH.